1. Field of the Invention
The present invention relates generally to catheters and, in particular, to catheters that are highly flexible yet resistant to crushing and kinking.
2. Description of the Related Art
Catheters have been developed and are commonly used for a wide variety of medical applications, including interventional therapy, diagnosis, drainage and the like. Catheters can be deployed to numerous target locations within a patient's body by guiding the catheter to the target location. For vascular procedures, catheters may be positioned with the aid of a separate guide wire. Catheters may also be positioned without using a guidewire by forming at least the distal portion of the catheter from a material that is sufficiently soft and flexible to follow blood flow.
Small diameter catheters are commonly used for diagnostic and interventional neurological procedures, such as the diagnosis and treatment of tumors, aneurysms, arteriovenous malformations, and the like. For example, catheters can be used to traverse small blood vessels in the brain vasculature, which are highly tortuous and require that at least a distal portion of the catheters be very flexible to accommodate such tortuosity.
Existing catheters, particularly those used to traverse a tortuous path through the body, suffer from a number of disadvantages. For example, the soft wall of the catheter needed to bend or curve the catheter often becomes crushed or kinked during use, and a small size and tight curvature of the catheter is difficult to achieve. Some manufacturers have used braided or helically wound wires or ribbons within the wall of the catheter to increase the tensile strength and crush resistance of the catheter. Examples of such catheters are disclosed in U.S. Pat. No. 5,954,651 issued to Berg et al., U.S. Pat. No. 5,947,940 issued to Beisel, and U.S. Pat. No. 6,702,972 issued to Markle. Other manufacturers have used slotted metal tubes within their shafts to provide a flexible catheter with good radial strength.
The existing catheters described above often have helical, braided, or other metallic elements embedded into the polymeric wall of the tubular body of the catheter. Such metallic elements create problems because they tend to separate or delaminate from the surrounding polymeric material, particularly in catheters having very thin walls. In an effort to overcome these problems, a catheter having a helical reinforcement element made of a hard polymeric material embedded in the tubular body of the catheter was developed by Follmer et al. and disclosed in U.S. Pat. No. 5,827,242. However, the helical reinforcement layer disclosed by Follmer et al. has not been totally effective in eliminating problems with kinking and crushing of the catheters, particularly in very small diameter catheters.
Thus, there is a need in the industry for an improved catheter that is highly flexible and yet resistant to crushing and kinking during use.